Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock options outstanding by exercise price range

The following summarizes information about stock options outstanding and exercisable at December 31, 2018:

	Options outstanding				Options exercisable
Range of exercise prices per share	Number outstanding	Weighted average exercise price per share		Weighted average contractual term (in years)	Number exercisable	Weighted average exercise price per share		Weighted average contractual term (in years)
$11.09 - 12.80	32,691	$	12.37	1.93	32,691	$	12.37	1.93
$13.20 - 16.24	26,669	15.73		4.00	26,669	15.73		4.00
$19.97 - 21.10	22,955	20.15		1.99	22,955	20.15		1.99
$23.78 - 25.14	162,561	24.59		3.59	162,561	24.59		3.59
$29.45 - 32.81	428,350	31.71		6.64	267,067	31.05		6.33
$46.95 - 53.72	104,217	53.35		8.25	43,842	53.54		8.24
$11.09 - 53.72	777,443	$	31.42	5.79	555,785	$	28.65	5.13

Summary of activity for Corporation's stock options

A summary of activity for the Corporation's stock options as of and during the years ended December 31, 2018, 2017 and 2016 is presented below:

	Non-vested stock options outstanding						Stock options outstanding
	Number of options		Weighted- average exercise price per share		Weighted- average grant date fair value per share		Number of options		Weighted- average exercise price per share
Outstanding at December 31, 2015	479,755		$	28.75	$	8.49	1,054,739		$	25.38
Granted	441,167		32.81		6.15		441,167		32.81
Acquired	—		—		—		1,466,408		15.08
Exercised	—		—		—		(450,296	)	20.02
Vested	(454,360	)	28.74		8.49		—		—
Forfeited/expired	(58,623	)	31.10		7.17		(58,623	)	31.10
Outstanding at December 31, 2016	407,939		$	32.81	$	6.15	2,453,395		$	21.41
Granted	132,414		53.43		9.94		132,414		53.43
Exercised	—		—		—		(1,427,159	)	17.50
Vested	(161,751	)	37.73		7.07		—		—
Forfeited/expired	(47,732	)	37.55		7.03		(47,732	)	37.55
Outstanding at December 31, 2017	330,870		$	37.97	$	7.09	1,110,918		$	29.56
Exercised	—		—		—		(302,796	)	24.00
Vested	(78,533	)	37.16		6.94		—		—
Forfeited/expired	(30,679	)	37.20		6.97		(30,679	)	37.20
Outstanding at December 31, 2018	221,658		$	38.37	$	7.16	777,443		$	31.42
Exercisable/vested at December 31, 2018							555,785		$	28.65

Assumptions of Black-Scholes option pricing model

The fair value of the stock options granted during the years ended December 31, 2017 and 2016 were estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions. The Corporation did not grant any stock options during the year ended December 31, 2018.

	2017			2016
Expected dividend yield	3.31		%	3.30		%
Risk-free interest rate	2.05		%	1.39		%
Expected stock price volatility	26.7		%	27.9		%
Expected life of options — in years	6.0			6.5
Weighted average fair value of options granted	$	9.94		$	6.15

Summary of activity for restricted stock units and awards

The following table provides information regarding nonvested restricted stock awards:

Nonvested restricted stock awards	Number of awards		Weighted-average acquisition-date fair value
Nonvested at January 1, 2018	83,228		$	46.23
Vested	(41,784	)	46.23
Forfeited	(592	)	46.23
Nonvested at December 31, 2018	40,852		$	46.23

A summary of the activity for RSUs during the year ended December 31, 2018 is presented below:

	Number of units		Weighted-average grant date fair value per unit
Outstanding at December 31, 2017	380,940		$	41.29
Granted	321,043		54.15
Converted into shares of common stock	(102,553	)	34.77
Forfeited/expired	(22,940	)	47.87
Outstanding at December 31, 2018	576,490		$	49.35